Planet 9

Does anyone know the purpose of the pipe that inter-connect the two mufflers on a Cayman S? Even the aftermarket units come with it... It seems add to me.

Is it for sound or performance?

What would happen if you delete it or block it and keep each engine bank independent from each other?

The muffler wouldn't like that. Here's a cutaway of the factory exhaust to help you see how the system works. Here's a post from another thread that will help you understand:

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Gator Bite
PCA Cayman Register Advocate

Thank you for the info... I've seen that thread @ Pelican.

That's the rason I asked the question here. It appears to me that there is a lot of turbulance and blockage in the CS system; however, most of the aftermarket systems have the by-pass pipe also - WHY? SOUND OR PERFORMANCE?

I believe, just like with Harley's that the interconnect pipe will lower the below or drone considerably. It allows the preassure to be equalized. All stock Harley exhausts have that interconnection until you get the after market straight pipes.

However, I believe that the stock Porsche exhaust is very efficient as is. You have to spend a lot of money to get any HP improvement that is consistentaly measurable and then in most cases you end up with drone.

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VIDS
Cayman Turbo 520HP

Reeeealllly....... I don't know if I should be flattered or pissed that they copied my work.

I am sure the little bypass pipe is completely for sound, to give the car the classic Porsche sports car song.


I have to respectfully and strongly disagree with the first part of that statement. I do not believe the stock exhaust is efficient. Keep in mind that I am a true mod skeptic who questions every claimed horspower gain (which has caused me some grief). I am also one who strongly believes that Porsche knows what their doing and that it's really hard to improve upon what they've done.

With that in mind, I have changed the exhaust system on my Cayman S no less than 6 times. I've rotated between Stock, Borla and AWE. Let me tell you this, every time I resinstall the stock system (2 times now), I am stunned at how choked the car feels above 5,000 RPMs. Every time I put the Borla or AWE back on, the first drive surprises me. The power gains are simply undeniable. I just reinstalled my AWE a few weeks ago, after having the stock system on there for several months. I came home and said to my wife, "Holy s---. I can't beleive the difference. Why the heck have I been driving around with the stock system on there....?" (My dyno runs consistently showed ~20 hp gained with each. My car performed 7+ runs with each, and with stock. The results were very consistent.).

I will agree with the second part of your statement. I haven't been in a Cayman with an aftermarket exast system that didn't have some drone in the 2,200 - 2,800 RPM area. Some worst than others. Some not so bad, some just downright loud. I believe the Capristo in cruise mode is the only system that present no real drone.

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Gator Bite
PCA Cayman Register Advocate

Well now you are comparing apples to oranges, an after market cat back not meeting any emmission standards to a OEM system. Sorry but the HP gains by cutting out a set of cats is in the 5-10HP range at best after deducting the margin of error of the dyno used. Adding to this drone, loss of legality, of course you get the awesome sound, I have to say the OEM system is very efficient as is. Doing it for looks and sound no question but the gains are nominal at best for a catback alone.

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VIDS
Cayman Turbo 520HP

Hey Gator Bite, no reason to be pissed by sharing info between us P-car owners - I believe it is awesome.

Regarding your experience with different systems, are u talking catback only or full units from the heads out (i.e. headers, reson, cats and catbacks).

Do they all have the interconnecting pipe?

Which one do you like most?

Gator: You should find the post and demand the mods give you credit for your work. Most of them are decent people and you shouldn't have to go through legal at all. A simple one-liner accrediting you is all you want, and most of the time the mods don't know the work is plagiarized.

OP: What would happen if you blocked the center pipe between them? Most probably nothing good. It'd totally change the harmonics of the exhaust and most likely not benefit flow.

Schwabe: A number of the systems on sale are street-legal. Your thesis is exceedingly hard to support. The stock exhaust is highly restrictive, it has been repeatedly proven that almost any exhaust mod will result in better high-rev power (clearly, caused by increased flow) including mods which do not delete cats, or replace them with more efficient units.

As you can see from the cut-out, the exhaust gas has to make at least one 180 turn in its path to get outside. This type of muffler is known as a variant of the "turbo type" muffler, and is widely held to be exceedingly bad for back-pressure. Although, this specific arrangement seems to be a fairly efficient variant of this design. In no way can it ever by anywhere near as efficient as the superior straight-through pipe most aftermarket exhausts use. Straight-through pipes, however, are very prone to loud drive-by and extremely prone to drone at some specific wavelength, which for the CS seems to be between 2400 and 2800 somewhere.

While there are certain after-market setups completely void of catalists, they're marked "Race Only" variants and are in no way what the bulk of Cayman Club modders use.

There is undeniable evidence: All exhausts except the stock one drone. All exhausts except the stock one make more power. Does this tell you the stock is more efficient? In making less noise, yes it does. In making power, nobody has ever correctly installed an exhaust from a reputable manufacturer and made less power.

I won't get into the whole honey-trap of "dynos are accurates/ nya-haah they ain't".

I am referring to catback systems. I've never changed my headers.

The AWE has an interconnecting pipe, but it functions much differently than the stock system. The Borla does not have an interconnecting pipe, it remains a true dual exhaust.


Well, you haven't convinced me. Once again, because of my personal experience. You seem very convinced of your last sentence. Tell me, have you ever had any quality aftermarket system on your Cayman? Is your theory backed by some kind of first hand experience?

I am a mod skeptic, and a dyno skeptic too. But I was there where they ran my car on the dyno. They did 7 pulls on my stock unmodified car. The first couple of runs were inconsistent, but then the last 4-5 were very consistent. They did the same with my Borla and AWE tests. They kept running the car over and over until it was spitting consistent numbers. The consistent numbers were the numbers used to quantify my results. Not the highest, not the lowest, the most consistent. And those results suggested that my car gained 21 BHP with the Borla, 19 with the AWE. Are those gains nominal? Mathematically, maybe 7% is nominal, but when I drive the car the after changing the system (either way), it doesn't feel nominal at all.

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Gator Bite
PCA Cayman Register Advocate

I can verify that the Capristo is drone free when in cruise mode. This system has no connecting pipe between the mufflers.

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Les

I'll deny it--the stock system on my '06 CS drones, from c. 2200 - 2600RPM, and I don't much like it.

Too bad all of this stuff is so expensive...but no one twisted my arm to buy the CS.

Yup, had a quality after market exhaust, had the SRP 4.1v, had UDP, had a K&N, and so on and so forth. You gave yourself the proof, 21HP gain, even giving you the full gain without deducting the error of the dyno, is less then 10% of what your car makes anyway. If you really feel that that makes a difference beyond the sound good for you. I am very sKeptic of anybody who claims they can feel a difference with less then a 25% gain. Again, all the listed aftermarket exhaust systems are illegal, maybe not in a particular state but certainly in California and more importantly in Germany. Again, 20HP may even be the difference between a bad and a very good running stock CS, we have seen stock dynos from 260 -285HP.

"Mathematically, maybe 7% is nominal, but when I drive the car the after changing the system (either way), it doesn't feel nominal at all."

Doesn't that say it all? Just like people swear by Lucas Oil and K&N and what not, all good and good for bragging rights certainly, most likely not making a difference on the road.

As for drone, the TPC exhaust is absolutely drone free.

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VIDS
Cayman Turbo 520HP

What do you think it'd happen if you block the interconnecting pipe?

There is another thread ongoing describing cutting an opening on the interconnecting pipe allowing a better sound and hopefully flow. Check it out.

It will likely hurt performance.

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Gator Bite
PCA Cayman Register Advocate

That is not normal. You should get that checked rather than suggest hundreds of us are tone-deaf to our stock exhausts!

Just kidding. But you should get it checked.

I think there is aproximately 0% chance it'll improve anything. I'd be interested to know how you intend to block the pipe without permanent damage to it. Constant high-volume flow of 650 degree hot gasses is not something you "block" easily.

The stock system will drone a bit under the right conditions if you run open throttle settings in these rpm ranges under load. Not a recommended thing. A downshift is prefered.

I wouldn't be surprised if blocking the crossover pipe would increase this. As a guess I suspect that one purpose the pipe serves to increase the effective length of the system which would lower the rpm that drone would occur. Sometimes balance or crossover pipes also increase power.

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Les

I've heard of cutting a notch on the crossover pipe by the connecting clamp to allow some pressure discharge and better sound... has anyone done it? Feedback?

Don't believe everything that you have heard. Especially when you get superior advice here. An aftermarket system will give you more noise, more hp and and annoying resonance at certain rpms. That is your best choice other than stock.

"...and annoying resonance at certain rpms..." That doesn't sound right. Is that a correct statement? Who wants the resonance?